Sony VAIO PCG-F540 Service Manual page 94

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Connecting an External Mouse or Keyboard
See “Using the Keyboard” on page 21 for more information on using the keyboard.
See the manual that came with your mouse or keyboard for more information on installation
and use.
Before you connect or disconnect the mouse or keyboard, turn off the computer.
Do not connect or disconnect the PS/2 device (keyboard or mouse) when the computer is on.
It may cause malfunction.
A Sony USB mouse PCGA-UMS1 (not supplied) is a USB device. You must connect it to the
USB connector.